| 摘要 |
PURPOSE: To remove nitrogen compounds in the drain of flue gas desulfurization by catalytic decomposition without causing a lowering of catalyst performance due to the generation of scale of gypsum or metal by a method wherein the flue gas desulfurization drain is softened to provide softened treated water, which is treated in the presence of catalyst to reduce nitric acid, and ammonia is oxidized in the presence of catalyst. CONSTITUTION: Alkali is added to flue gas desulfurization drain in a softening treatment tank 1, while the drain is being agitated, thereby to adjust pH to, for example, 11 or more, and carbonate is added thereto and further flocculant is added. The treated water, in which metal hydroxide and calcium carbonate are deposited and coagulated, is sent to a concentration device 2, where supernatant liquid is sent to a filter 4 by a pump 3, and then pH of the water is adjusted to, for example, 6-8 at a pH adjusting tank 5. Thereafter, water is sent to a catalyst packed tower 9A via a heat exchanger 7 and a heater 8, in which reducing agent is added to water to reduce nitric acid ion. The treated water which leaves the tower A9 and to which an oxidizing agent is added on piping way is sent to a catalyst packed tower B10, where ammonium ion is oxidized. |
